average by group

Hola!

Try this...

=AVERAGEX(
	FILTER(
		Table1,
		Table1[Year] = EARLIER(Table1[Year])
	),
	Table1[Plan Sales Amount]
)

yukon 

is it some running average? it looks like you have an error in Excel

if you need average from all groups by year try a measure

Average Plan Sales Amout by Group (Year) =
CALCULATE(AVERAGE(Table[Plan Sales Amount]), ALLEXCEPT(Table, Table[Year]) )

or column from littlemojopuppy  solution

yukon 

Average by group can be done in ways in DAX, like this above answers. However, I think the data you provided is not correct for some reason. How can you get different values when you average. Maybe check your excel files and also provide the formula you used so we can see what are you calculating to get that expected result.

Usually, you get average by group(year) with column or measures using:

RESULT = CALCULATE(AVERAGE([Plan Sales Amount]), ALLEXCEPT(Table,[Year]))

Best regards
Paul Zheng